By Dagan: (NaturalNews) Metabolism refers to the physical and chemical processes that synthesis energy. These chemical reactions take place within the cells with help from enzymes and hormones. This process converts food and oxygen to the energy needed to run the body. Increasing the metabolism increases energy and enables weight loss. Everyone's metabolism is different and this is largely determined by genetics. Your metabolism is also influenced by your age, and it slows down by 5% each decade after age 40.